Open Source Maintainer / Core Contributor – Software Engineer

$150/hr

rate as listed

Workload: 40 hrs/week
Engagement: Project-based
Location: US
Field: STEM and Coding

Design repository-grounded engineering tasks, reference solutions and tests using a mature open-source project you maintain or substantially contribute to. Review AI-written code and grading rubrics while working a full-time, exclusive weekday engagement through Cincinnatus LLC.

The work

You will turn real maintenance work from a mature, widely used open-source repository into challenging features, refactors and bug fixes for AI training. Day to day, that includes writing reference solutions, evaluating AI-generated code and tests, checking grading rubrics, running the project locally with Docker, and explaining technical shortcomings in your own words.

What the screening emphasizes

Mercor will look for a public, verifiable record of sustained contribution through your own GitHub account. You must qualify either as a maintainer named in MAINTAINERS or CODEOWNERS, or through at least 10 pull request reviews in the last 12 months, or as a core contributor with at least 3 substantive merged pull requests in the last 12 months. The relevant repository must be at least two years old, primarily human-written, actively reviewed and used by real users. Expect follow-up on repository architecture, review decisions, testing strategy and edge cases in AI-written changes.

Logistics

This is a 40-hour-per-week W-2 position with Cincinnatus LLC, with work performed on weekdays and on an exclusive basis. During the engagement, you cannot hold another full-time role or participate in another AI training or evaluation project, including another Mercor project. You must be authorized for U.S. W-2 employment, complete required background checks and confidentiality agreements, and use a company-provided device. The listing does not specify whether the role is remote, how much work is asynchronous or the required daily working hours.

Pay band: $150/hr

What they look for

Verifiable maintainer or core contributor status in a widely used open-source project
Senior-level review of code, tests, edge cases and repository conventions
Ability to design realistic engineering tasks and accurate reference solutions
Local project setup, test execution and Docker-based validation
Sustained public open-source contribution history on the candidate's own GitHub account
Precise written technical rationales and feedback

Included with this listing

Interview prep — 10 questions

Matched to what this platform's screening actually measures. Answer each out loud in 60–90 seconds: claim → concrete example → implication.

What it tests: This verifies your relationship to one qualifying repository through named ownership, recent review activity or recent substantive merged pull requests.
A strong answer: Identify the repository, your GitHub account, its age and users, and the exact public artifacts that establish your status. Distinguish substantive code ownership from minor documentation, formatting or dependency-only changes.
Where people lose it: Candidates lose points by discussing open source generally without giving repository links, qualifying review counts, merged pull requests or named ownership evidence.

Summary, eligibility guidance and screening preparation are prepared by Sidequest from the platform's posting. Check the source listing before applying.

STEM AND CODING on Sidequest

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